The field of the invention is imaging and measurement systems. More particularly, the present invention relates to a system and method for acquiring a three-dimensional surface image of an object using a range camera.
A number of 3D range cameras have been introduced commercially in the last two years. In many fields ranging from computer-aided design and manufacturing to the entertainment and fashion industries, it is desirable to obtain a computer model of an object""s surface geometry quickly and inexpensively. Range cameras are relatively inexpensive and easy to use compared to other three-dimensional imaging devices, such as X-ray machines. Range cameras can measure the range or distance from the camera to thousands of points distributed over the surface of an object in one xe2x80x9cexposurexe2x80x9d or snapshot. The result of the exposure is a computer file containing X, Y and Z coordinates of the sampled 3D points lying on the surface of the object. Some of these cameras work like a box camera, in which the camera points and shoots the object with fixed resolution and field of view. Other cameras are more complex and offer the ability to change optical parameters such as stand-off distance, focal distance, field-of-view and minimum/maximum range depth without moving the camera. To cover a large object, it may be necessary to acquire and merge many range images into a mosaic or composite set of points in such a way that there is an acceptable level of resolution and accuracy achieved.
Given an object to be measured, it is a complex task to determine the number of images required and the values of the optical parameters for each exposure. Without assistance, an operator experimentally determines a reasonable selection of vantage points and camera settings. Each selection typically must be verified via a test exposure of the camera, which comprises the steps of setting up the camera, setting the parameters into the camera, taking images, reviewing results, readjusting and repeating the steps, if necessary. Due to the involved interaction between optical parameters, it is often very difficult for the operator to predict the resultant resolution and accuracy of the total scan. Therefore, it becomes necessary to perform laborious trial and error approaches to achieve the desired appearance of the image.
What is desired is a system that will address some of the problems previously described with the use of range cameras. What is also desired is a system that automatically determines a scanning plan for a range camera including optimal view locations and a set of camera parameters for each view. What is also desired is a system that will automatically control the camera to acquire the collection of 3D images. There is a need for a system to acquire scan data having a level of resolution so that when the scan data is merged to form the three-dimensional surface image, the surface image has acceptable accuracy and resolution for a given application.
A method of acquiring a three-dimensional surface image of an object using a range camera automatically calculates an optimal number of scans. The optimal number of scans is calculated in accordance with operator-defined and camera optical parameters. Scan data acquired for each scan is merged with a preference for higher resolution data over lower resolution data for any given scanned area, such that the merged scan data forms the three-dimensional surface image of the object.
A system for acquiring a three-dimensional surface image of an object includes a range camera controlled to automatically calculate a scanning plan in accordance with operator-defined parameters and camera optical parameters.